Advanced Line Following

[tatwood]

Advanced line following involves a course with zig-zags, broken lines and criss-crossing lines. This is a particularly interesting "next step" in line following competition developed by the Chibots club in Chicago. I'd like to open the discussion with the following question, but any relevant question is fair game for any who wish to join this thread. What are the dimensions and characteristics of an advanced line-following course, what kinds of breaks and criss-crosses have figured in past competitions that make for the best challenge, distances defining breaks, and are there any sure-fire best platforms/sensor combos to start with? Thanking in advance any who comment--

Tom Atwood
toma@botmag.com

[wrighthobbies]

The advanced line following contest is an attempt to challenge the more experienced robot builders. The course has offset gaps in the line, tight zigzags, a point where the line crosses itself and obstacles like a hill or uneven surfaces which we experimented with at our last contest.

The vision based robots excel at this type of course. Using the AVRCam, the bots can see much further ahead and pretty much ignore the zigzags, the line width variations and the gaps. The obstacles can pose more of a challenge since vision robots tend to put the camera above the robot, making it taller than most and a little top heavy. As long as the obstacles don't have a height restriction (like a tunnel), then the vision bots can usually navigate them.

[TheDuck]

When it isn't vision-based, is the typical line sensor a light and a sensor that measures the reflection? More reflection = white, less = black? Can you have these sensors outboard of the robot? Or is there something in the way of ambient light concerns that make it more effective tucked under the robot?

And now onto my hare-brained scheme....

Imagine a line-follower with some arbitrary number of 'feelers' with light sensors on the ends that range around the robot! That would have to be a pretty freaky sight!

[wrighthobbies]

Hehe, that could be a little unsettling to see...

You are correct on the light sensors, the light reflected, the more "white" it is. Keep in mind that reflected IR (which most light sensors use) may not correlate to visible light. You may see black and white but the robot may see just black or just white. Masking tape is a good example. While it looks rather white to us, an IR sensor doesn't see it.

The sensors are sometimes outboard but not by much. There are size limits that keep you from having the sensors too far out. I'd have to look at the rules again to see if it's ok to have deployable sensors that increase the size of the bot.